(a) Field of the Invention
The present invention relates to liquid crystal displays (LCDs) and more particularly to a thin film transistor array panel and a method of repairing an LCD including the same.
(b) Description of Related Art
LCDs are one of the most widely used flat panel displays. An LCD includes two panels having field-generating electrodes with a gap interposed therebetween. A liquid crystal (LC) layer fills the gap between the panels. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer, which determines orientations of LC molecules in the LC layer to adjust polarization of incident light.
The LCD includes a plurality of pixels arranged in a matrix and a plurality of signal lines for driving the pixels, such as gate lines for transmitting scanning signals and data lines for transmitting data signals. Each pixel includes a pixel electrode, a thin film transistor (TFT) connected to the gate lines and the data lines for controlling the data signals, and a storage electrode forming a storage capacitor along with the pixel electrode for maintaining the data signals for a predetermined time.
The defects in an LCD, which increase the manufacturing cost of the LCD, include pixel defects. Pixel defects include a white defect, in which a pixel is in a permanent white state, and a black defect, in which a pixel is in a permanent black state.
The white defect is caused by poor contact between the pixel electrode and the TFT or by a malfunction of the TFT, which initially makes a corresponding pixel to be in a black state and then makes the pixel to be in a white state in a normally white mode LCD since current leakage makes the voltage of the pixel electrode on one panel equal to a common voltage of a common electrode on the other panel. Another cause of the white defect is a short circuit between a pixel electrode and a data line or a common electrode caused by conductive particles. Since the white defect is easily noticed by human eyes while the black defect is not, it is preferable that the white defect be changed into the black defect. For example, the white defect can be repaired or changed by connecting the corresponding pixel electrode to a gate line or a storage electrode.
The connection between the pixel electrode and the gate line or the storage electrode can be obtained by laser illumination from a TFT array panel or from a common electrode panel. The laser illumination from the TFT array panel that is adjacent to a backlight unit requires the disassembling of the LCD for separating the backlight unit or a chassis. The illumination from the common electrode panel easily damages color filters and black matrix on the common electrode panel, thereby causing the strip of the common electrode or the short circuit between the common electrode and a pixel electrode, thereby decreasing the reliability of the repair. When the color filters are disposed on the TFT array panel, the thick color filters obstruct the electrical connection between the pixel electrode and the gate line or the storage electrode and the color filters tend to come off from the bottom.